STROBE Statement—checklist of items that should be included in reports of observational studies
Item
No. Recommendation
Page No.
Relevant text from manuscript Title and abstract 1 (a) Indicate the study’s design with a commonly used term in the title or the abstract 1
(b) Provide in the abstract an informative and balanced summary of what was done and what was found
2-3
Introduction
Background/rationale 2 Explain the scientific background and rationale for the investigation being reported 4-5
Objectives 3 State specific objectives, including any prespecified hypotheses 5
Methods
Study design 4 Present key elements of study design early in the paper 5 Setting 5 Describe the setting, locations, and relevant dates, including periods of recruitment, exposure,
follow-up, and data collection
6-7
Participants 6 (a) Cohort study—Give the eligibility criteria, and the sources and methods of selection of participants. Describe methods of follow-up
Case-control study—Give the eligibility criteria, and the sources and methods of case ascertainment and control selection. Give the rationale for the choice of cases and controls Cross-sectional study—Give the eligibility criteria, and the sources and methods of selection of participants
6
(b) Cohort study—For matched studies, give matching criteria and number of exposed and
1
unexposed
Case-control study—For matched studies, give matching criteria and the number of controls per case
Variables 7 Clearly define all outcomes, exposures, predictors, potential confounders, and effect modifiers.
Give diagnostic criteria, if applicable
7
Data sources/
measurement
8* For each variable of interest, give sources of data and details of methods of assessment
(measurement). Describe comparability of assessment methods if there is more than one group 7 Bias 9 Describe any efforts to address potential sources of bias NA Study size 10 Explain how the study size was arrived at NA
Continued on next page
Quantitative variables
11 Explain how quantitative variables were handled in the analyses. If applicable, describe which groupings were chosen and why 7-8 Statistical
methods
12 (a) Describe all statistical methods, including those used to control for confounding 8 (b) Describe any methods used to examine subgroups and interactions 8 (c) Explain how missing data were addressed
(d) Cohort study—If applicable, explain how loss to follow-up was addressed
Case-control study—If applicable, explain how matching of cases and controls was addressed
Cross-sectional study—If applicable, describe analytical methods taking account of sampling strategy NA
(e) Describe any sensitivity analyses NA
Results
Participants 13* (a) Report numbers of individuals at each stage of study—eg numbers potentially eligible, examined for eligibility, confirmed eligible, included in the study, completing follow-up, and analysed 6+8 (b) Give reasons for non-participation at each stage NA
(c) Consider use of a flow diagram NA Descriptive
data
14* (a) Give characteristics of study participants (eg demographic, clinical, social) and information on exposures and potential confounders 8-9
(b) Indicate number of participants with missing data for each variable of interest NA (c) Cohort study—Summarise follow-up time (eg, average and total amount)
Outcome data 15* Cohort study—Report numbers of outcome events or summary measures over time
3
Case-control study—Report numbers in each exposure category, or summary measures of exposure Cross-sectional study—Report numbers of outcome events or summary measures 8 Main results 16 (a) Give unadjusted estimates and, if applicable, confounder-adjusted estimates and their precision
(eg, 95% confidence interval). Make clear which confounders were adjusted for and why they were included NA (b) Report category boundaries when continuous variables were categorized NA (c) If relevant, consider translating estimates of relative risk into absolute risk for a meaningful time period NA
Continued on next page
Other analyses 17 Report other analyses done—eg analyses of subgroups and interactions, and sensitivity analyses 8
Discussion
Key results 18 Summarise key results with reference to study objectives 15 Limitations 19 Discuss limitations of the study, taking into account sources of potential bias or imprecision. Discuss
both direction and magnitude of any potential bias 17 Interpretation 20 Give a cautious overall interpretation of results considering objectives, limitations, multiplicity of
analyses, results from similar studies, and other relevant evidence 15-17 Generalisability 21 Discuss the generalisability (external validity) of the study results 17
Other information
Funding 22 Give the source of funding and the role of the funders for the present study and, if applicable, for the original study on which the present article is based 19
*Give information separately for cases and controls in case-control studies and, if applicable, for exposed and unexposed groups in cohort and cross-sectional studies.
Note: An Explanation and Elaboration article discusses each checklist item and gives methodological background and published examples of transparent reporting. The STROBE checklist is best used in conjunction with this article (freely available on the Web sites of PLoS Medicine at http://www.plosmedicine.org/, Annals of Internal Medicine at http://www.annals.org/, and Epidemiology at http://www.epidem.com/). Information on the STROBE Initiative is available at www.strobe-statement.org.
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